Background: FR901464 is a novel and potent antitumor antibiotic that exhibits prominent effects against both murine and human solid tumors. FR901464 strongly activates an SV40-driven reporter gene at low nanomolar concentrations and regulates the expression of several cancer-related genes in human cells. Despite the unique and promising biological activity of FR901464, its biological mechanisms remain to be elucidated. Objective/Hypothesis: A firm understanding of the mode of action of FR901464 will pave the way for the development of a new approach for cancer therapy. To understand the mode of action of FR901464, the target biomolecules of FR901464 need to be isolated. In this proposal, we aim to chemically synthesize FR901464 and its analogs for biological studies and use a radio-labeled FR901464 analog to isolate the target biomolecules. Specific Aims: (1) To study the chemical reactivity of FR901464 by using simple model systems;(2) to design and synthesize more stable FR901464 analogs, which will be studied in following two aims;(3) to determine the specificity of FR901464 analogs toward human tumor cell lines and normal cells and to investigate their effects on transcriptionally regulated cellular targets by high-content analysis;and (4) to isolate and characterize intracellular targets of FR901464. Study Design: First, we will study the chemical reactivities of FR901464 under biologically relevant conditions. In this study, each reactive moiety of FR901464 will be used to unambiguously analyze the results. Based on the chemical insight gained from this study, we then focus our synthetic efforts on developing stable and potent FR901464 analogs. These analogs will then be tested with various cancer cell lines to elucidate the structure-activity relationships (SAR) of FR901464. We will also perform high-content analysis to monitor various parameters (transcriptional activity, DNA damage, apoptosis, etc.). This analysis will provide more advanced insight into the specificity of FR901464 and its analogs. Finally, we will prepare radio-labeled FR901464 analogs to isolate the targets of FR901464 in live cells. Significance: The isolation of the targets of FR901464 will have significant impacts on anticancer drug development, as we envision several pharmaceutical companies will begin to look for other drugs that bind these therapeutic targets for cancer treatment.